Popcorn is often mass-produced for sale at movies and other events in commercial popcorn poppers which generally include an enclosed, transparent cabinet containing a tiltable kettle suspended above a catch area or platform. The kettle is heated and uncooked popcorn kernels are placed therein to be cooked and popped. Oil, salt and other flavorings might also be added to the kettle for flavoring the popcorn in the popping process. Once the kernels are popped, the kettle is tilted, either manually or automatically, and the popcorn spills onto the platform to be scooped up, packaged, and sold to customers. More recently, and especially as home movie theaters have gained in popularity, popcorn poppers have begun to move into the residential market for residential consumption as well. In the residential market, the residential popcorn poppers are often used to make smaller batches of popcorn than those made in commercial environments.
Conventional kettles require that fasteners be welded to the bottom thereof to mount a heating element thereupon. For example, FIG. 1 illustrates a prior art kettle 10 having an upstanding side wall 12 and a bottom wall 14. A plurality of machined, threaded fasteners 16 are welded to the bottom wall 14 of the kettle 10 so that a threaded shaft or shank of each fastener 16 extends downwardly from the bottom wall 14 of the kettle 10. Each fastener 16 is machined such that its head is reduced in size and has at least four sides, with the head of each fastener being welded to the kettle bottom.
During welding of the fasteners 16 to the kettle 10, a number of defects may occur because of the small surface area with which to attach the fasteners 16 to the bottom 14 of the kettle 10. Specifically, an undercut defect often occurs, which removes a portion of the machined portion of the fastener 16 and creates a stress area in the form of a notch, which may amplify stress concentrations. A notch in a fastener 16 may eventually widen and/or otherwise continue through the fastener 16 and cause at least a portion of that fastener 16 to fall off.
A weld may also be weakened or destroyed by simply overtightening the fastener 16 during assembly. Given that the head of the fastener 16 is rigidly affixed to the kettle 10, the torque applied to the fastener 16 transmits directly to the weld. Should too much torque be applied, the weld may be forced to failure immediately or over some period of use. In either case, the failure may again cause at least a portion of the fastener 16 to fall off.
Should the weld fail such that the fastener 16 falls off, there may be a loss in structural integrity of anything held thereby, including a heating element (not shown in FIG. 1) secured to the kettle bottom by the fasteners 16. Moreover, a short circuit in the kettle heater may occur when a fastener 16 falls off, as that fastener 16 may short across the heating element, and/or wires connected to the heating element. A fastener 16 that has fallen off the bottom 14 of the kettle 10 can increase popcorn cooking times and/or decrease the efficiency of a cooking cycle. Furthermore, it is often expensive and time-consuming to fix a kettle 10 after a fastener 16 has fallen off, as the kettle 10 must be machined down to a uniform surface at the location of the missing fastener 16. The kettle 10 must then be stripped of all chrome, a new fastener 16 must be welded to the kettle bottom, and then the kettle must be re-chromed. This process often takes a number of days or even weeks and may be associated with a substantial cost due to repairs, loss of income, and lost opportunities, as a popcorn popper with no kettle is typically useless.
After assembling a conventional kettle, as is set out above, other problems may be encountered during operation of the kettle. For example, maintaining the proper temperature of a cooking surface within the kettle while popping popcorn is critical for producing quality popcorn for consumer consumption. On one hand, should the temperature of the cooking surface be too low, many kernels may fail to pop; thus producing significant waste. On the other hand, should the temperature of the cooking surface be too high, there is a risk of igniting the oil in the mixture and/or burning the popped popcorn within the kettle.
Measuring the temperature of the cooking surface so that it may be controlled, is not, however, without difficulty. The heated mixture of kernels, salt, and oil on the cooking surface is extremely abrasive. While it would be ideal to measure the temperature of the mixture directly, positioning a sensor in direct contact with such a salty, abrasive environment tends to destroy temperature sensors, such as thermocouples. For this reason, temperature sensors are often positioned on the external surface of the kettle and are thus separated from the mixture by the kettle wall. Thermal conduction through the kettle wall allows indirect measurement of the cooking surface and the mixture. The exterior surface of the kettle, particularly the bottom surface of the kettle, is often difficult to access due to its assembly with the heating element, which leaves little room in which to place a temperature sensor along this surface. In addition, the side wall of the kettle is prone to unintended contact with the remaining portion of the popcorn popping machine or even an operator during use. Thus, locating a temperature sensor to assure accurate temperature measurement is problematic.
Therefore, there is a need for an improved popcorn popping kettle that overcomes these and other shortcomings and drawbacks of known popcorn popping kettles.